G. Nawrat

Structure Modification of Surface Layers of Ti6Al4V ELI Implants

In the work, the influence of electrochemical modifications of Ti6Al 4V ELI on the in vitro corrosion resistance was studied. The specimens with carbon lay er produced with the use of IBAD method on the passivated specimens were also examined. The char acteristics of the grinded, the electropolished, the electropolished and electrochemically passiva ted and with the passivecarbon layer specimens were evaluated by the potentiodynamic tests in Tyrode’s solution. A flexibility of the passive layer was examined in potentiodynamic tests of the bended specimens. Results show that electropolishing and anodic oxidation in the examined s olutions increased the in vitro corrosion resistance of the alloy. The corrosion potential of t he polished and passivated specimens is much higher then the grinded samples. The increase of pa sive current density was not observed for the polished and passivated specimens. The passive layer wa s uniform that was proved by the AFM investigation. The tests proved high corrosion resistance of the passivated specimens that were bended (up to 90 °) to evaluate the flexibility of passive layer. The passive-car bon layer ensures corrosion resistance, which is not as high as for passivated samples. Introduction Titanium and its alloys are corrosion resistant biomaterials tha t are characterized by a wide passive range [1, 2, 3]. The breakdown potentials are higher then membrane potential s of ssue in a living body (0,2-0,45V)[4]. It should be assumed that the loss of passivity in the el ectrochemical fluids and tissue system is rather impossible. However, a passive layer can be mechanically or chemically damaged. Metallic surface is then uncovered and corrosion processes ar e initi ted. Currently the scientific research is focused on surface layer modification te chniques in order to increase the corrosion resistance of implants. It should be said that implants underg o plastic deformation. For this reason prepared layers should be characterized by the plastic deforma tion ability. The aim of the work was to work out conditions of producing passive-carbon layers on Ti6Al4V ELI alloy surface and the evaluation of the corrosion resistance. Materials and methods Ti6Al4V ELI was used in the research. Chemical composition and mecha nical properties met the ASTM standard [5]. Surface preparation involved: grinding, electrochemic al polishing, anodic oxidation and carbon layer creation with the use of double beam method I on Beam Assisted Deposition (IBAD) [6]. Electrochemical polishing was carried out i n the bath composed of: sulfuric acid (20÷70% vol.) + hydrofluoric acid (20 ÷50% vol.) + ethylene glycol (10 ÷20% mass) + acetanilide (20% mass). Anodic oxidation was carried out in the soluti on of CrO3 – 100÷200g/litre. The specimens were passivated at different potentials. The corrosi on resistance of layers was evaluated by potentiodynamic method in the Tyrode’s solution (36,6 ±1°C and pH=6,9÷7,5). NonKey Engineering Materials Online: 2003-12-15 ISSN: 1662-9795, Vols. 254-256, pp 387-390 doi:10.4028/www.scientific.net/KEM.254-256.387

Reduced Graphene Oxide Supported Antimony Species for High-Performance Supercapacitor Electrodes

Antimony species was chemically anchored on graphene oxide using antimony (III) chloride precursor and then converted to the reduced graphene oxide-antimony species composite by a well-established polyol method. The resultant composite was successfully used as supercapacitor electrodes in a two-electrode symmetric system with aqueous electrolyte. The specific capacitance calculated from the galvanostatic charge/discharge curves obtained for this composite was 289 F/g. The enhanced capacitance results were confirmed by the electrochemical impedance spectroscopy and cyclic voltammetry. The high capacitance of the reduced graphene oxide-antimony species composite arises from the combination of double-layer charging and pseudocapacitance caused by the Faradaic reactions of the intercalated antimony species and residual surface-bonded functional groups.

Stripping of copper coatings from steel in Cr(VI)-free commercial bath

In this work the electrochemical characteristics of copper and steel in chromate, cyanide, and phosphate baths as well as in a commercial bath (ENSTRIP S-180), in the absence of chromium and cyanides were determined. Average rates of copper coatings stripping from steel in the above mentioned baths and the baths influence on the morphology of steel surfaces were described. It was found that the commercial bath ENSTRIP S-180 could be successfully used for stripping of copper coatings from steel elements.

Corrosion Study of Amorphous Mg67Zn29Ca4 Alloy

The aim of this paper was investigating the corrosion resistance of Mg67Zn29Ca4 metallic glass and evaluating the ability of use studied amorphous alloy for medical applications as biodegradable implants. For comparative purposes the corrosion studies of the amorphous Mg67Zn29Ca4 samples were performed in a few simulated body fluids at 37°C. The immersion tests were performed in Ringer’s solution, PWE (multielectrolyte physiological fluid) and 3%NaCl water solution. The amount of evolved hydrogen[ml/cm2] and a corrosion rate Vcorr [g/(day·m2)] of studied Mg67Zn29Ca4 alloy were compared. Surface morphology of metallic glass after corrosion study was performed using the scanning electron microscopy.In aim determination dissolution rate and amount of evolved hydrogen was simulated the environment of human body fluids during immersion tests. The work presents structure characterization and corrosion properties analysis of Mg67Zn29Ca4 bulk metallic glasses in the form of plates. Samples structure was analyzed by means of X-ray diffraction. Fractographic study a cross section of the sample in plates form was performed using scanning electron microscopy

Microplasma Oxidation of Magnesium Alloy AZ91D by Impulse Current

In this work the results of investigations on thickness distribution of conversion coatings on magnesium alloy AZ91D obtained by plasma electrolytic oxidation (PEO) in sodium silicate solution are presented. The morphology and chemical composition as well as thickness distribution of obtained coatings, with special respect to hard to reach points are shown. Also the corrosion resistance of obtained alloy samples is determined.

The Influence of Deposition Process on Structure of Platinum-Modifed Aluminide Coatings O Ni-Base Superalloy

The modern jet engines used in commercial and military aircrafts are characterized by operating temperature in turbine section above 1000oC. The Ni-base superalloy turbine blades and vanes working in high temperature in very aggressive environment require using of protective coatings. The aluminide coatings are widely used to protect this engine parts. The pack cementation, out of pack and chemical vapour deposition (CVD) technologies are usually used to produce this type of coating. The aluminide coatings can be modified by platinum or other elements. The Pt-modified aluminide coatings are characterized by better oxidation and corrosion resistance in comparison with conventional aluminide coatings and can be used as a bond coat for Thermal Barrier Coatings deposited by EB-PVD technology. In present study the influence of deposition technology and their’s parameters on structure and chemical composition of Pt-aluminide coatings are presented. The base material for coatings was a Inconel 738 Ni-base superalloy. The first step of coatings production were Pt electroplating with different thickness of platinum layer. The second step of coating production was aluminising process. The aluminide coatings were produced by pack cementation and out of pack technologies. Additional the influence of heat treatment of base alloy with coatings was investigated. The structure of all deposited coatings was observed by scanning electron microscopy and the chemical and phase composition of coatings were investigated by EDS and XRD methods. The observed coatings were characterized by two types of structure: first based on NiAlPt phase obtained on thin Pt layer and the second with additional presence of PtAl2 phase on the thick Pt layer.

Effect of temperature and pH of ammonium galvanic bath on the properties of Zn-Co alloy coatings

The results of investigations on Zn-Co coatings obtained electrochemically in acidic and neutral ammonium baths are presented. The chemical composition, morphology and surface roughness of received coatings were determined together with the current efficiency. It was found that the coatings morphology depends on the process parameters. In the case of neutral bath the increase of bath temperature resulted in decrease of cobalt contents in the coatings, whereas it was not practically observed for acidic baths. It was also observed that surface roughness of the Zn-Co coatings decreased with the increase of temperature for both types of baths. It was also found that the grain size of coatings obtained in neutral bath depends on pH of bath.